1. Field of the Invention
The present invention relates to a metal V-belt type continuously variable transmission including an endless belt which has a large number of metal elements mounted on a metal ring and which is wrapped around a pair of pulleys.
2. Description of the Related Art
A metal V-belt type continuously variable transmission has already been proposed in Japanese Patent Application Laid-open No. 9-264390 by the present assignee, wherein the inclination angle .alpha. of the V-groove in the pulley is set in a range of tan.sup.-1 .mu.a&lt;.alpha.&lt;tan.sup.-1 .mu.s, wherein .mu.s represents a static friction coefficient between the pulley and a metal element, and .mu.a represents a dynamic friction coefficient between the pulley and the metal element, whereby the tensile force of the endless belt is decreased by making the inclination angle .alpha. of the V-groove small, and the transmittable torque is increased while avoiding the slipping of the endless belt.
When the metal V-belt type continuously variable transmission performs shifting, if a movable pulley half is moved away from a stationary pulley half, the metal elements are moved radially inwards to decrease an effective radius of the pulley. If the movable pulley half is moved toward the stationary pulley half, the metal elements are moved radially outwards to increase the effective radius of the pulley. In this case, when the distance of radial movement of the metal elements is greater, the ratio can be set in a larger range. For this reason, it is desirable that the length of the side of the element contacting with a V-face of the pulley is decreased to ensure a large movable distance of the metal elements. However, if the element side length is decreased, there is a possibility that a hertz surface pressure acting between the pulley and the metal element may be increased to influence the durability.